A particle detecting device including a liquid particle counter or a flow cytometer includes a flow cell for allowing a fluid, which is a sample, to flow therethrough. The flow cell is transparent. When the fluid flowing through the flow cell is irradiated with inspection light, particles contained in the fluid fluoresce or cause scattered light. Fluorescence or scattered light is focused with a lens disposed adjacent to the flow cell, and detected. On the basis of detected results such as the number of times fluorescence or scattered light is detected, the intensity of detected fluorescence or scattered light, and the wavelength of detected fluorescence or scattered light, the number or type of particles contained in the fluid can be specified. For example, whether the particles are viable particles, whether the particles are resin, or whether the particles are air bubbles can be determined.
At the time of shipment or periodical inspection, a particle detecting device undergoes inspection of, for example, the position of an inspection light source, an optical path of inspection light including the incident position or the angle of incidence of inspection light on the flow cell, the focal point of inspection light, and the position of the flow cell. The positions or angle deviating from the designed values are adjusted.
For example, PTL 1 describes a method for detecting the peak of scattered light having a wavelength the same as that of a laser beam by moving a condensing lens or a capillary cell to cause the laser beam to appropriately enter the capillary cell. PTL 2 describes a method for detecting scattered light having a wavelength the same as that of a laser light beam generated by particles flowing through the flow cell by moving the position of the flow cell relative to a laser light source to adjust the position from which a laser light beam is emitted. PTL 3 describes a method for irradiating the flow cell through which particles flow with a laser light beam and capturing an image of scattered light generated by the particles and having a wavelength the same as that of the laser light beam to adjust the positions of the optical system and the flow cell.